Technical challenges for capacitors

Traditional electrolytic capacitors were not able to meet the market trends for low ESR. Today PEDOT, is widely used in the capacitor industry to manufacture polymer type tantalum and aluminum capacitors to meet these challenges.

For more than 20 years, applications of aluminum and tantalum capacitors have been driven by low ESR (Equivalent Series Resistance) requirements. Traditional electrolytic capacitors were not able to meet these requirements of modern electronic circuits like motherboards.

Clevios™ Conductive polymers enabled capacitor manufacturer to meet the market trends for low ESR. Today, because of its high conductivity and outstanding temperature stability, the conductive polymer poly (3,4-ethylenedioxythiophene), also known as PEDOT, is widely used in the capacitor industry to manufacture polymer type tantalum and aluminum capacitors.

However, the application field of polymer capacitors was limited to consumer electronics mainly due to the lack of high voltage capability, relatively high DC leakage current (DCL) and low reliability performance.

Heraeus’ development of Clevios K™ polymer dispersions has overcome these restrictions of polymer capacitors. Now for the first time, high voltage, low DCL and high reliability applications could be accessed. The rated voltage range of polymer capacitors has been extended from maximum of about 25 V to 400 V. In combination with a superior DCL performance, the new polymer capacitors have been introduced in high reliability applications like automotive. Today, polymer capacitors are even promoted for aerospace applications which was unimaginable in the past. Low ESR and high ripple current capability allow to downsize electronic circuits by using smaller capacitors or by replacing a number of bulky electrolytic capacitors with a single polymer capacitor.

The technology move to high voltage, low DCL and high reliability was enabled by Heraeus’ development of new conductive polymers for capacitor applications. Conductive polymers are used as cathode material in polymer capacitors. A conductive polymer film is deposited on the dielectric which was formed by anodization of a porous aluminum or tantalum electrode. For a long time, chemical in-situ polymerization methods had to be applied to form such a conductive polymer cathode film. Precursors of conductive polymers, monomer (Clevios™ M V2) and oxidizer (Clevios™ C), are introduced into the porous capacitor body and the cathode is formed by a chemical reaction within the device. The development of Clevios K™ conductive polymer dispersions allows for a direct deposition of the conductive polymers without any chemical in-situ reaction. Thus, not only the performance and reliability of the capacitor is boosted but the capacitor manufacturing process is simplified significantly at the same time.

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